- re-fixed FTexture::CheckTrans

The original broken code had it always reset the translucency info to 'not present'.
The first fix completely removed that line, although it was merely misplaced, but still necessary to avoid constant re-checking of the same texture.

src/gl/textures/gl_texture.cpp

@@ -520,6 +520,7 @@ void FTexture::CheckTrans(unsigned char * buffer, int size, int trans)
 					return;
 				}
 			}
+			gl_info.mIsTransparent = 0;
 		}
 	}
 }